How to measure the power consumed by a C algorithm while running on a Pentium 4 processor?

Question

How can I measure the power consumed by a C algorithm while running on a Pentium 4 processor (and any other processor will also do)?

Answer 1

Run your algorithm in a long loop with a Kill-a-Watt attached to the machine?

Answer 2

Hi

Excellent question; I upvoted it. I haven't got a clue, but here's a methodology:

-- get CPU spec sheet from Intel (or AMD or whoever) or see Wikipedia; that should tell you power consumption at max FLOP rate;

-- translate algorithm into FLOPs;

-- do some simple arithmetic;

-- post your data and calculations to SO and invite comments and further data

Of course, you'll have to frame your next post as another question, I'll watch with interest.

Regards

Mark

Answer 3

Unless you run the code on a simple single tasking OS such as DOS or and RTOS where you get precise control of what runs at any time, the OS will typically be running many other processes simultaneously. It may be difficult to distinguish between your process and any others.

Answer 4

First, you need to be running the simplest OS that supports your code (probably a server version unix of some sort, I expect this to be impractical on Windows). That's to avoid the OS messing up your measurements.

Then you need to instrument the box with a sensitive datalogger between the power supply and motherboard. This is going to need some careful hardware engineering so as not to mess up the PCs voltage regulation, but someone must have done it.

I have actually done this with an embedded MIPS box and a logging multimeter, but that had a single 12V power supply. Actually, come to think of it, if you used a power supply built for running a PC in a vehicle, you would have a 12V supply and all you'd need then is a lab PSU with enough amps to run the thing.

Answer 5

It's hard to say.

I would suggest you to use a Current Clamp, so you can measure all the power being consumed by your CPU. Then you should measure the idle consumption of your system, get the standard value with as low a standard deviation as possible.

Then run the critical code in a loop.

Previous suggestions about running your code under DOS/RTOS are also valid, but maybe it will not compile the same way as your production...

Answer 6

Sorry, I find this question senseless.

Why ? Because an algorithm itself has (with the following exceptions*) no correlation with the power consumption, it is the priority on the program/thread/process runs. If you change the priority, you change the amount of idle time the processor has and therefore the power consumption. I think the only difference in energy consumption between the instructions is the number of cycles needed, so fast code will be power friendly. To measure power consumption of a "algorithm" is senseless if you don't mean the performance.

*Exceptions: Threads which can be idle while waiting for other threads, programs which use the HLT instruction.

Sure running the processor at fast as possible increases the amount of energy superlinearly (more heat, more cooling needed), but that is a hardware problem. If you want to spare energy, you can downclock the processor or use energy-efficient ones (Atom processor), but changing/tweaking the code won't change anything.

So I think it makes much more sense to ask the processor producer for specifications what different processor modes exist and what energy consumption they have. You also need to know that the periphery (fan, power supply, graphics card (!)) and the running software on the system will influence the results of measuring computer power.

Why do you need this task anyway ?

Answer 7

hey guys thanks for replying.... The code is a very simple C code( not even 150 lines) so I guess we can easily run it under DOS.... I need to do this for my college project and they are insisting on not using any external device or circuitry... Isn't there any way to do it logically.. by just using some operating system commands or something else of that sort..... I looped my code for 10000 times and the number of clock ticks required were 845 and the time required was 46.428570...Cant we perform some manipulation on these values and get some fair idea on the power consumed..... If you want I can upload the whole code

Answer 8

Since you know the execution time, you can calculate the energy used by the CPU by looking up the power consumption on the P4 datasheet. For example, a 2.2 GHz P4 with a 400 MHz FSB has a typical Vcc of 1.3725 Volts and Icc of 47.9 Amps which is (1.3725*47.9=) 65.74 watts. Since you know your loop of 10,000 algorithm cycles took 46.428570s, you assume a single loop will take 46.428570/10000 = 0.00454278s. The amount of energy consumed by your algorithm would then be 65.74 watts * 0.00454278s = 0.305 watt seconds (or joules).

To convert to kilowatt hours: 0.305 watt seconds * 1000 kilowatts/watt * 1 hour / 3600 seconds = 0.85 kwh. A utility company charges around $0.11 per kwh so this algorithm would cost 0.85 kwh * $0.11 = about a penny to run.

Keep in mind this is the CPU only...none of the rest of the computer.